* {
	margin: 0;
	padding: 0;
}

:root {
	--title-height: 30px;
}

.app {
	display: flex;
	flex-direction: column;
	height: 100vh;
}

.app .title {
	text-align: center;
	height: var(--title-height);
	line-height: var(--title-height);
}

.app .btn {
	display: flex;
	justify-content: space-evenly;
	margin: 10px 0;
	height: 25px;
}

.app .btn .active {
	text-decoration: underline;
	background-color: red;
}

.app .content {
	flex: 1;
	overflow: overlay;
}
